Wafer bonding involves aligning two wafers parallel to each other, bringing them in contact with each other and then applying heat and force to the aligned stack of the two wafers. Referring to FIG. 1, in a wafer bonder apparatus 210, a first wafer 30 having a bond layer 32 on a first surface 30a is brought into contact with a second wafer 20 having a bond layer 22 on a first surface 20a, so that the two bond layers 31 and 22 are opposite to each other. The wafer bonding process involves orienting the two wafers parallel to each other and compressing the two wafers together by applying a force 220 on a second surface 30b of the first wafer 30. Force 220 is usually applied to the center of the wafer stack 30 with a piston-type mechanism. This bonder apparatus provides precise wafer bonding and is suitable for bonding one wafer pair at a time. In some applications, however, it is desirable to bond several wafer pairs at once in order to increase bonder throughput and to reduce device cost. Accordingly, there is a need for a high throughput industrial scale wafer bonder apparatus for bonding several wafer pairs at once.